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Re: [PATCH] Erase the distinctClause if the result is unique by definition - Mailing list pgsql-hackers

From Andy Fan
Subject Re: [PATCH] Erase the distinctClause if the result is unique by definition
Date
Msg-id CAKU4AWqi8_N+13+msrDOK1HZhLppSY0RN9gxESYFKzjKmX4E1w@mail.gmail.com
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In response to [PATCH] Erase the distinctClause if the result is unique by definition  (Andy Fan <zhihui.fan1213@gmail.com>)
Responses Re: [PATCH] Erase the distinctClause if the result is unique by definition  (Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>)
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update the patch with considering the semi/anti join. 

Can anyone help to review this patch?  

Thanks


On Fri, Jan 31, 2020 at 8:39 PM Andy Fan <zhihui.fan1213@gmail.com> wrote:
Hi:

I wrote a patch to erase the distinctClause if the result is unique by 
definition,  I find this because a user switch this code from oracle 
to PG and find the performance is bad due to this,  so I adapt pg for
this as well. 

This patch doesn't work for a well-written SQL,  but some drawback 
of a SQL may be not very obvious,  since the cost of checking is pretty
low as well,  so I think it would be ok to add.. 

Please see the patch for details.   

Thank you. 
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